Research and Application of Log Defect Detection and Visualization System Based on Dry Coupling Ultrasonic Method

In order to optimize the wood internal quality detection and evaluation system and improve the comprehensive utilization rate of wood,this paper invented a set of log internal defect detection and visualization system by using the ultrasonic dry coupling agent method.The detection and visualization analysis of internal log defects were realized through log specimen test.The main conclusions show that the accuracy,reliability and practicability of the system for detecting the internal defects of log specimens have been effectively verified.The system can make the edge of the detected image smooth by interpolation algorithm,and the edge detection algorithm can be used to detect and reflect the location of internal defects of logs accurately.The content mentioned above has good application value for meeting the requirement of increasing demand for wood resources and improving the automation level of wood nondestructive testing instruments.

Design of a hexagonal air-coupled capacitive micromachined ultrasonic transducer for air parametric array

An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great potential for air-coupled applications,mainly because of their low acoustic impedance.In this study,an air-coupled CMUT array is designed as an air parametric array.A hexagonal array is proposed to improve the directivity of the sound generated.A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell.The CMUT array is then fabricated by a wafer bonding process with high consistency.The performances of the CMUT are tested to verify the accuracy of the finite element analysis.By optimizing the component parameters of the bias-T circuit used for driving the CMUT,DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission.Finally,the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.

Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory

This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.

Non-Contact Velocity Measurement of Japanese Cedar Columns Using Air-Coupled Ultrasonics

The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the axial direction (VL) showed the minimum values around the pith. The averaged VL increased from 3600 m/s towards the outside of measurement area and attained the maximum values (=4010 m/s). The velocities in the lateral direction (VRT ) showed no tendency among measurement points. The averaged VRT was 1450 m/s. The velocities obtained using the non-contact method showed a significant positive relationship with those obtained using the contact method. The averaged ratio of VL to VRT was measured to be approximately 2.2 to 2.8. These ratios were in agreement with those from a contact method. These findings suggest that it is possible to measure the velocity in Japanese cedar columns with the non-contact method by using air-coupled ultrasonics.

Research Review of Principles and Methods for Ultrasonic Measurement of Axial Stress in Bolts

Bolts are important fasteners indispensable in the manufacturing field for their advantages, which include convenient assembly and disassembly, easy maintenance, refastenability to prevent looseness, and the avoidance of a phase change in the connected material composition. The precise control of the tightening force in bolts is closely related to the safety and reliability of the connected equipment or structure. Although there are many methods for estimating the tightening force applied to a bolt during assembly, poor accuracy in controlling the preload during the tightening process and a lack of monitoring to determine the residual axial force in service remain issues in evaluating the safety of bolted assemblies. As a nondestructive testing technology, ultrasonic measurement can be applied to successfully address these issues. In order to help researchers understand the theoretical basis and technological development in this field and to equip them to conduct further in-depth research, in this review, the basic knowledge describing the state of stress and deformation of bolts, as well as conventional testing methods are summarized and analyzed. Then, through a review of recent research of the ultrasonic measurement of the axial stress in bolts, the influence of the e ective stressed length and temperature are analyzed and proposed methods of calibration and compensation are reviewed. In order to avoid coupling errors caused by traditional piezoelectric transducers, two newly proposed ultrasonic coupling technologies, the electromagnetic acoustic transducer(EMAT) and the permanent mounted transducer system(PMTS), are reviewed. Finally, the new direction of research of the detection of residual axial stress in in-service bolts that have been assembled to yield is discussed.

Effect of alternating ultrasonic frequency electric signal on the distribution of pore in aluminum alloy weld

The application of ultrasonic vibration in the welding process can effectively suppress the pore defects of the weld.The different ultrasonic application methods own different effects on the weld pore.In this paper,the ultrasonic frequency vibration in the weld pool is excited by the coupling of the ultrasonic frequency electrical signal and the welding electrical signal.The influence of ultrasonic excitation voltage and excitation frequency on porosity,number,location,and size of pore in weld was investigated.The results show that the variation of ultrasonic excitation voltage and frequency has a direct influence on the pore distribution.The pore defects can be decreased by the coupling of ultrasonic frequency electrical signal with reasonable parameters or increased by the coupling of ultrasonic frequency electrical signal with unreasonable parameters.The ultrasonic excitation frequency is fixed at 30 kHz and the ultrasonic excitation voltage is changed.The porosity of the weld is close to that of the weld without ultrasonic action when the ultrasonic excitation voltage is 25 V and 75 V.The porosity of the weld is significantly lower than that of the weld without ultrasonic action when the ultrasonic excitation voltage is 50 V and 100 V.The ultrasonic excitation voltage is fixed at 100 V and the ultrasonic excitation frequency is changed.The porosity of the weld is the largest and exceeds that of the weld without ultrasonic action when the ultrasonic excitation frequency is 20 kHz.The porosity of the weld is lower than that of the weld without ultrasonic action when the ultrasonic excitation frequency is 25,30,35,and 40 kHz.The pores were mainly concentrated on the upper part of the weld and the number of pores of small size increased significantly after the coupling of an ultrasonic frequency electrical signal,indicating that ultrasonic promoted the rise and escape of bubbles in the weld pool.

Characteristics of ultrasonic vibration transmission in bonding process

The transmitting models of ultrasonic vibration in ultrasonic transducer and capillary were presented according to the propagating mechanism of ultrasonic wave in elastic body. The coupling characteristics of ultrasonic longitudinal-complex transverse vibration system were simulated by Matlab software. The ultrasonic vibration displacement and the velocity of high frequency were measured by using the PSV-400-M2(1.5MHz) laser Doppler vibrometer. The vibration locus shapes driven by the same frequency and different frequencies were tested by using GDS-820S dual channel digital oscilloscope. The microstructures at bonding interface were observed by means of KYKY2800 scanning electron microscope. The results show that ultrasonic vibration displacement or velocity and energy density increase with the decrease of section area in the transmitting process. The vibration locus shapes driven simultaneously by the same frequency and different frequencies are elliptical (or circular) loci and rectangular (or square) loci, respectively. And the characteristics at bonding interface are improved by coupling loci.

EXPERIMENTAL RESEARCH ON THE ULTRASONIC TECHNIQUE AND ITS APPLICATION IN STUDYING ROCK PROPERTIES

The experimental installation and measurement system of ultrasonic wave property in rocks during complete stress-strain process were established and perfected. The interrelations between ultrasonic wave property of mudstone,sandstone and limestone specimens during complete stress-strain process and their mechanic property were investigated. A new type of device for the observation of surrounding rock stability--borehole ultrasonic device with completely dry coupling was developed to get better coupling and more accurate measurement data comparing with those of water coupling situation. Preliminary study on the application of ultrasonic measurement technique at belt conveyor roadway of north wing in Baodian Coal Mine (Shandong province) was conducted. Based on the interrelations between the complete stress-strain properties of specimens and their wave properties, the structural properties of surrounding rocks, the range of yield zones,and the change of stresses within surrounding rocks when a Iongwall face was across over the roadway were analyzed. Therefore,a new and feasible way was found for the research on the deformation law of surrounding rock of roadway and rational selection of support parameters.

STUDY ON MECHANISM OF ARC-EXCITED ULTRASONIC

A mechanism of excited arc to be an controlled “ultrasonic emission source” is described. An developed electrical source with an certain frequency bandwidth for the purpose of the arc excited is connected with an conventional welding power supply through coupling the cables for the experiment. Some resonant frequency bands for the arc excited ultrasonic are discovered in the welding process, and its frequency, amplitude and phase'shift are recorded. This principle demonstrates that arc can be used not only for a thermal source, but also for an ultrasonic emission source, which may be extent to the industrial application in some new ways, such as for automatic welding process control and quality inspection.

Intelligent Control Algorithm of PTZ System Driven by Two-DOF Ultrasonic Motor

It is difficult for the traditional pan-tilt-zoom(PTZ)system driven by electromagnetic motor to meet the growing demand for video surveillance system.The key challenge is high positioning accuracy,high dynamic performance and miniaturization of the PTZ system.Here a PTZ system driven by two degree-of-freedom obeliskshaped ultrasonic motor with single stator is presented,and its intelligent control algorithm is studied.The structure and driving mechanism of the presented PTZ system are analyzed by both simulation and experiment.To solve the complex nonlinear factors,e.g.time-variation,dead zone,the fuzzy PID control algorithm and the variable gain cross-coupled control strategy are combined to improve the control performance.The results show that the proposed algorithm has faster response,higher precision than traditional control algorithm,and it also has a good robustness to prevent the effect of interference.

基于空耦超声激励的微结构模态频率温度特性研究

为了研究微悬臂结构弯曲振动模态频率的温度特性,首先针对各向异性材料的等截面矩形微悬臂结构建立了其各阶模态频率温度系数的理论模型;然后搭建了包括激光测振单元、空耦超声激励单元和温度控制单元的非接触式微结构动态特性测试系统;最后利用所搭建的测试系统分别对等截面矩形单晶硅微悬臂梁在室温~300℃时的动态特性进行了测试,获得了微悬臂梁前三阶弯曲振动模态频率随温度的变化规律和频率温度系数。研究结果表明,单晶硅微悬臂梁前三阶弯曲振动模态频率随着温度的升高而呈近似线性的减小,并且微悬臂梁前三阶弯曲振动模态具有几乎相同的频率温度系数,其中一阶模态频率的温度系数为-2.18×10-5/℃,二阶模态频率的温度系数为-1.91×10^(-5)/℃,三阶模态频率的温度系数为-2.01×10^(-5)/℃,前三阶模态频率温度系数的测试结果与理论模型预测值的偏差分别3×10^(-7)/℃,3×10^(-6)/℃和2×10^(-6)/℃。

可溶性钾盐主要成分分析前处理技术与分析方法研究

钾盐是中国最紧缺的矿产资源之一,为农业三大肥料中钾肥的主要原料,当前具有开发利用价值的主要是可溶性钾盐资源。而目前可溶性钾盐尚无国家标准物质和标准分析方法,本文对称样量、固液比、溶解温度、溶解时间、搅拌条件、超声时间和功率等条件进行实验研究,利用电热板和超声振荡两种溶解方式,建立了可溶性钾盐中主要成分钾、钠、钙、镁、氯和硫酸根离子的分析方法。采用电感耦合等离子体发射光谱仪测定样品中的Ca^(2+)、Mg^(2+)、K^(+)和Na^(+)的含量,离子色谱仪测定样品中Cl^(-)和SO_(4)^(2-)的含量,两种溶解方法分析可溶性钾盐样品中上述离子的实验结果基本吻合。电热板溶解方法精密度为0.52%~3.19%(RSD,n=11),超声振荡溶解方法精密度为0.55%~3.07%(RSD,n=11),两种方法检出限为0.01~0.05μg/g。利用主要成分百分含量加和、加标回收率、阴阳离子平衡验证方法准确性,两种溶解方法的主要成分加和在99.0%~101.0%之间,加标回收率在95.3%~103.8%,阴阳离子平衡在-3%~3%之间,均满足DZ/T 0130.3—2006质量管理规范中的分析要求。两种可溶性钾盐的溶解方法均可在日常检测中应用,对于较大批的钾盐样品分析,电热板溶解法整体工作效率较高,更适用于实验室内批量样品分析;超声振荡器溶解方法与电热板溶解方法相比,更为简单快速,对于少量样品的分析,效率更高,且超声波振荡器方便野外携带,使用在钾盐的野外现场勘探工作中,可较大地提高工作效率,实时指导找矿行动顺利开展。

铝管与泡沫层胶接结构脱黏缺陷的空气耦合超声检测

针对铝管与泡沫隔热层胶接结构脱黏缺陷的检测问题,开展了检测技术研究和脱黏缺陷类型分析。根据胶接结构的特点,制作了人工缺陷试样,使用空气耦合超声穿透法进行C扫描成像检测,并对扫描发现的异常区域进行微焦点CT检测分析,归纳了脱黏缺陷的类型及其成因。试验结果表明,空气耦合超声穿透法能有效检出材料中的脱黏缺陷,脱黏缺陷的成因包括型面不贴合引起胶层未填满和胶层内空气未完全排出产生了间隙层。

大尺寸三维超声振动系统的智能优化设计

对大尺寸三维超声换能器系统的耦合振动进行有效控制,优化系统的性能,一直都是功率超声领域亟待解决的难题.研究发现,一些声子晶体槽、孔结构可以对大尺寸换能器系统的横向振动进行抑制,提高系统振幅分布均匀度,且可以通过改变声子晶体结构的配置参数人为地实现对大尺寸三维超声振动系统性能的调控.但过多的设计参数必然会增加系统设计的复杂度,且目前大尺寸三维超声换能器系统的优化设计依赖于经验试错法,设计效率和成功率较低,性能也无法保证.研究引入同质位错、点缺陷结构对大尺寸三维超声振动系统进行优化设计,并利用数据分析技术评价了同质位错、点缺陷结构的配置对系统辐射面的纵向位移振幅、振幅分布均匀度、辐射声功率、工作带宽等的影响规律,建立了同质位错结构、近周期缺陷结构的结构参数——大尺寸超声换能器系统性能的预测模型,实现了对大尺寸功率超声换能器系统的智能设计,提高了设计效率和成功率,降低了设计成本.

盐酸超声提取-高分辨电感耦合等离子体质谱法测定食用植物油中11种微量金属元素

提出了盐酸超声提取-高分辨电感耦合等离子体质谱法(HR-ICP-MS)快速测定食用植物油中铝、钡、镉、铜、铁、镁、锰、镍、铅、钒、锌等微量金属元素的方法。取2.0 g食用植物油样品,置于50 mL塑料离心管中,加入800μL ICP溶剂油,于旋涡混匀器上充分混匀,加入10 mL 2.0 mol·L^(-1)盐酸溶液,于70℃超声30 min,冷却。以转速10000 r·min^(-1)离心5 min,在水相与有机相分离后,收集水相,采用HR-ICP-MS测定其中11种元素含量,待测同位素^(51)V、^(56)Fe、^(27)Al、^(63)Cu、^(24)Mg、^(55)Mn、^(60)Ni、^(66)Zn选择中分辨率模式,而^(137)Ba、^(111)Cd和^(208)Pb选择低分辨率模式。结果表明:11种元素的质量浓度在100μg·L^(-1)以内与对应的信号强度呈线性关系,检出限(3s)为0.012~0.173μg·L^(-1);按照标准加入法对食用植物油进行回收试验,回收率为86.9%~107%,测定值的相对标准偏差(n=7)为1.1%~4.9%;方法用于分析3种植物油样品,本方法测定值与标准方法的测定值基本一致。

偏硼酸锂熔融-酒石酸络合-超声提取-电感耦合等离子体原子发射光谱法测定岩矿型锆矿石中10种元素的含量

为实现岩矿型锆矿石样品中锆、铪、钾、钙、钠、镁、铝、铁、钛、锰等10种元素含量的准确测定,优化了熔融、提取等试验条件,提出了题示方法。取干燥后的样品0.1 g于铂坩埚中,加入0.5 g偏硼酸锂,搅匀后盖上坩埚盖,于1 000℃熔融30 min。冷却后将铂坩埚置于装有25 mL含20 g·L^(-1)酒石酸的20%(体积分数)盐酸溶液中,超声振荡至熔块完全溶解,用水定容至100 mL,用电感耦合等离子体原子发射光谱仪测定。结果显示:上述10种元素的质量浓度分别在一定范围内与对应的谱线强度呈线性关系,检出限(3s)为1.90~40.8μg·g-1;方法用于由锆含量较低的基性岩岩石标准物质和锆精矿标准物质复配成的以锆石、斜锆石为主的岩矿型锆矿石样品的分析,测定值的相对误差为-1.9%~4.0%,测定值的相对标准偏差(n=12)为0.46%~4.5%,准确度和精密度试验结果的绝对值均优于DZ/T 0130.3-2006规定的控制指标,且方法可拓展应用于砂矿型锆矿石的准确测定。

标准GB/T 7233.1-2023中几处问题的探讨

通过对GB/T 7233.1—2023相关条款的讨论,对标准中用词欠妥、声束直径、耦合传输修正测定等内容提出了不同的观点,并提出了修改建议,有助于该标准的进一步完善。

空气耦合超声检测复合材料研究综述

复合材料普遍具有高比强度、高比刚度、高模量、耐腐蚀等优异性能,广泛应用于飞机机翼、导弹外壳、航空发动机壳体等部位。制造和服役过程中各类缺陷影响复合材料的力学性能和服役性能,必须采用有效的方法准确检测和评估复合材料中各类缺陷。空气耦合式超声检测具有完全非接触、非侵入、无损伤和无需耦合剂的特点,能够很好地运用于复合材料的在线和在位检测。该文就近年来空气耦合超声检测技术的研究现状进行了系统综述,简明扼要地分析和介绍了当前空气耦合超声检测的研究热点及进展,重点介绍了1-3型压电复合材料换能器、信号处理技术、相控聚焦式空气耦合超声检测、超声在复合材料的传播特性及其与缺陷交互作用的研究现状,探讨了空气耦合超声无损检测技术与仪器的发展方向,总结了目前空气耦合超声检测的研究热点问题,最后展望了空气耦合超声检测的发展趋势和应用前景。

超声王水浸提-电感耦合等离子体质谱(ICP-MS)法测定土壤中汞的含量

为建立了一种适合土壤中汞含量测定的方法,通过考察样品前处理中使用的王水体积、超声温度、超声时间和超声功率以及测定过程中的干扰消除等因素对测定的影响,确定了0.1 g土壤样品中加入5 mL的王水溶液,放入超声波清洗器中在功率400 W、60℃水浴下超声浸提30 min的前处理方法;电感耦合等离子体质谱仪通过^(209)Bi作为内标,仪器采用KED模式消除质谱干扰;提出了将金溶液与内标试剂共同配制,从而形成在线冲洗消除记忆效应的方法。结果表明:汞浓度在0~20μg/L内线性良好,相关系数R=0.99946;方法检出限为1.5μg/kg,方法定量下限为6μg/kg;通过测定值与认定值对比分析可知测定结果均在认证值范围内,方法准确度较高;RSD为2.1%~3.4%(n=6),方法精密度较高,满足分析要求。超声王水浸提-电感耦合等离子体质谱法测定土壤中的汞含量,前处理易操作,普适性强,准确度和精确度均满足检测要求,可适用于大批量土壤汞含量测定工作。

高效液相色谱-电感耦合等离子体质谱法测定畜禽肉中5种砷形态的含量

提出了高效液相色谱-电感耦合等离子体质谱法(HPLC-ICP-MS)测定畜禽肉中三价砷[As(Ⅲ)]、五价砷[As(Ⅴ)]、二甲基砷(DMA)、一甲基砷(MMA)、砷甜菜碱(AsB)等5种砷形态含量的方法。取样品1.000 g,加入10 mL含1%(体积分数)硝酸的10%(体积分数)甲醇溶液(提取剂),于60℃超声提取2.0 h。冷却,离心,分取5 mL上清液,加入5 mL正己烷,振摇1 min,离心10 min,弃去上层正己烷相,再加入5 mL正己烷重复上述步骤1次。吸取下层清液,过0.45μm有机滤膜。以Agilent ZORBAX SB-Aq色谱柱(250 mm×4.6 mm,5μm)为分离柱,以含5 mmol·L^(-1)己烷磺酸钠的20 mmol·L^(-1)柠檬酸溶液(pH 4.3)为流动相进行等度洗脱滤液中的目标物。结果表明:5种砷形态标准曲线的线性范围均为2~50μg·L^(-1),检出限(3S/N)为0.1~0.2μg·L^(-1);对实际样品进行3个浓度水平的加标回收试验,5种砷形态的回收率为81.5%~101%,测定值的相对标准偏差(n=6)为1.3%~3.6%。方法用于10份实际样品分析,其中As(Ⅲ)、DMA和AsB的检出率较高,肝脏、肾脏中的砷形态检出量高于肌肉中的,但均远低于GB 2762—2017对肉及肉制品中总砷的限量(0.5 mg·kg^(-1))要求。